This contract supports the coordination and subcontracts to the 28 clinical centers that follow participants of the Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications (EDIC) study. The DCCT was conducted during 1983-93 for an average of 6.5 yrs in 1441 type 1 diabetic participants age 13-39 years from 29 clinical centers in the U.S. and Canada. The DCCT demonstrated the beneficial effects of intensive therapy aimed at achieving glycemic levels as close to the nondiabetic range as possible, compared with conventional therapy, on retinopathy, nephropathy, and neuropathy. Intensive therapy consisted of one basal insulin injection and three pre-prandial short-acting doses of insulin, or use of an insulin pump, and self-monitoring of blood glucose at least four times per day. Conventional therapy consisted of one or two injections of insulin per day. Average HbA1c during the DCCT in the intensive therapy group was 7.0% and in the conventional therapy group was 9.0%. Following the end of the DCCT in 1993 and a transitional period when the conventional treatment group was taught intensive therapy and the clinical care of all subjects was transferred to their own health care providers, the observational study titled the EDIC was launched at 28 clinical centers. HbA1c in the two treatment groups quickly converged to about 8.0%. The primary goal of EDIC is to determine the long-lasting effects of the previously assigned therapies, based on an intention-to-treat analysis, on diabetic complications. Those complications that require longer time to develop than the original DCCT period of follow-up, including more advanced microvascular complications and cardiovascular disease, are of particular interest. Approximately 95% of the surviving DCCT participants are being followed and collection of complete data is maintained on greater than 90% of the cohort after long-term follow-up.